Ontogenetic formation of the ability of rats to count time endogenously and its relationship with the level of anxiety.

Improvements in the ability to count time endogenously with maturation in rats depends on the normal age dynamics of anxious-phobic state and is associated with the state of the peripheral compartment of the sympatheticoadrenal system. Increases in the lengths of locomotive excursions were accompanied by decreases in anxious-phobic state and increases in the quality of time-keeping. In rats aged three and six months (but not in one-month-old rats), the ability to count time endogenously showed a parabolic relationship with initial anxious-phobic state: the most precise and efficient counting of time intervals needs a certain intermediate level of anxiety, covering a relatively narrow range. Anxious-phobic states beyond this optimum, either increases or decreases, lead to degradation of chronometric ability.